feat: add retry-after header support

[nicdard]

Description

• Extend retries to 429 by default
• Support parsing of retry-after header and use the time specified there when available instead of the exponential backoff strategy
• Add tests to cover the new features

Related Issue

Motivation and Context

This feature is used to better handle retries.

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• I have signed the Adobe Open Source CLA.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[codecov]

Codecov Report

Merging #22 (1b3e820) into master (762fc54) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master       #22   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            5         5           
  Lines          113       134   +21     
  Branches        22        30    +8     
=========================================
+ Hits           113       134   +21     

Impacted Files	Coverage Δ
src/HttpExponentialBackoff.js	100.00% <100.00%> (ø)
src/utils.js	100.00% <100.00%> (ø)

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[nicdard]

What's the normal workflow? Should I rebase on top of new master or simply update the branch with merge?

[sangeetha5491]

The changes look good . Will also wait for @shazron to approve